Calculation of the remaining lifetime of power transformers paper insulation

Abstract

Abstract-This paper presents the remaining lifetime calculation of power transformers paper insulation and consequently of power transformers. The calculations are performed based on two models, which are related to the thermal degradation of the cellulose winding paper insulation: the common IEC loading guide and a paper degradation model. The paper insulation model's prediction can be improved by involving data from furfural analysis. The remaining lifetime is extracted from the fault probability (reliability) of the paper insulation. The two models are brought together, to aid the asset manager in the decision making process. A probabilistic approach is used, which can be coupled to analysis in terms of risks, benefits, costs, and availability by the asset manager.

Fourier Transform Infrared (FTIR) Spectroscopy Analysis of Transformer Paper in Mineral Oil-Paper Composite Insulation under Accelerated Thermal Aging

“…As shown in these figures, it is clear that the peak absorbance value of the O-H functional group located close to 3329 cm −1 decreases with aging due to the oxidation process. The products of degradation of cellulose paper are CO, CO 2 , H 2 O, H 2 , CH 4 , and furans, which are dissolved in the mineral oil [28]. During thermal aging, the cleavage of cellulose chains involves an O-H functional group.…”

“…Cellulose is a homopolymer of D-anhydroglucose units bonded together with C1-C4 glycosidic oxygen linkages [2]. Cellulose paper plays an important role in considering the lifetime of power transformers [3][4][5]. Cellulose has been characterized by the degree of polymerization (DP), which is the average number of glucose rings of its polymeric chain [6,7].…”

Study on the Effects of Thermal Aging on Insulating Paper for High Voltage Transformer Composite with Natural Ester from Palm Oil Using Fourier Transform Infrared Spectroscopy (FTIR) and Energy Dispersive X-ray Spectroscopy (EDS)

“…Figure 1b shows the Hitachi SU 3500 and EDAX system used for the EDS measurements. Figure 2 shows the reduction of the DP of transformer insulation paper with aging at the temperatures of 120 • C and 150 • C. The DP indicates the number of C 6 H 10 O 5 glucose rings that compose the cellulosic macromolecule and it is the valuable indicator that provides information about the degradation state of cellulose and mechanical strength [24]. It is seen that the DP has decreased faster at 150 • C than at 120 • C. At about 140 • C, the rate of the degradation process increases significantly, implying either a change in the activation energy or in the pre-exponential factor [25].…”

“…Figure 2 shows the reduction of the DP of transformer insulation paper with aging at the temperatures of 120 °C and 150 °C . The DP indicates the number of C6H10O5 glucose rings that compose the cellulosic macromolecule and it is the valuable indicator that provides information about the degradation state of cellulose and mechanical strength [24]. It is seen that the DP has decreased faster at 150 °C than at 120 °C .…”

Comparative study between conventional and hybrid solid insulation systems

“…Therefore, the degradation of paper used in power transformer insulation systems is attributed to the oxidation and hydrolysis reactions only. Moreover, oxidation reactions are more significant because their activation energy value is lower than the activation energy of hydrolysis [8]. Under the combined action of oxygen and temperature, many by-products are formed which can be used to indicate the level of degradation in paper insulation.…”